1. Field of the Invention
The invention relates to a rolling bearing unit for a wheel.
2. Description of the Related Art
For example, Japanese Patent Application Publication No. 1-276070 (JP-A-1-276070) and Japanese Patent Application Publication No. 3-6458 (JP-A-3-6458) each describe a rolling bearing unit that supports a wheel of, for example, an automobile. The bearing unit described in each of JP-A-1-276070 and JP-A-3-6458 includes an outer ring member that is fixed to a vehicle body-side member, an inner ring member that is rotatably fitted in the outer ring member, and double-row rolling elements that are arranged between the outer ring member and the inner ring member in such a manner that the rolling elements are able to roll therebetween. In the bearing unit described in each of JP-A-1-276070 and JP-A-3-6458, a plurality of flange portions is formed on the outer periphery of the outer ring member in such a manner that the flange portions project outward from the outer periphery. The bearing unit is fixed to a vehicle suspension with bolts that are fitted in bolt-holes formed in the flange portions.
Various loads such as a vehicle weight are applied to the outer ring member via the rolling elements. However, in existing bearing units such as the bearing units described in JP-A-1-276070 and JP-A-3-6458, the circumferential location of the flange portions is determined based on the location of bolt-holes formed in the vehicle body-side member. That is, there has been no bearing unit in which the circumferential location of flange portions is determined with the rigidity of an outer ring member taken into account.